A semiconductor manufacturing process includes a process of selectively etching and removing a SiN (silicon nitride) film on a substrate in which the SiN film and a SiO2 (silicon oxide) film are exposed. As an etching method for selectivity etching the SiN film, Patent Document 1 describes a technique of heating an etching solution containing hydrogen fluoride (HF), sulfuric acid (H2SO4) and water (H2O) up to a boiling point temperature thereof and performing an etching process by using the heated etching solution. However, in Patent Document 1, in order to shorten a processing time, an etching rate needs to be higher, and a ratio (selectivity) of an etching rate of the SiN film to an etching rate of the SiO2 film is not sufficiently high.
Patent Document 1: Japanese Patent Laid-open Publication No. 2002-246378 (Claim 16, paragraphs [0093] to [0098] and FIG. 18)